I remember NOVA did an episode "Secrets of the Viking Sword" (a sort of sequel to a similar episode about Japanese sword making traditions) where a modern black

I remember NOVA did an episode "Secrets of the Viking Sword" (a sort of sequel to a similar episode about Japanese sword making traditions) where a modern blacksmith created a sword using presumed methods from the viking era to create a crucible steel sword. They pointed out the advantages that the better metallurgy would provide; I remember them showing the sword flex while most contemporary swords would have broken. The idea was that this was sort of a trade secret for steel production and so it was rare and this may be one of the sources for legends of "magic swords".